The present invention relates to an optical unit to which an imaging optical system is detachably attached, an imaging unit, an imaging body, and an imaging device.
There is known a camera capable of exchanging an imaging element with another imaging element of a different size according to the purpose (refer to Patent Document 1). This camera has a horizontally-long box-like camera body and a photographing lens for silver salt single-lens reflex camera. As the camera body, a camera body for silver salt single-lens reflex camera is used without modification. As a back lid, one for silver-salt camera and one for digital camera are prepared. When the back lid for digital camera is attached to the camera body, this camera can be used as a digital camera. Further, this camera has a configuration allowing exchange of a CCD substrate and thus different types of digital cameras can be realized by one camera body.    Patent Document 1: JP-A-2000-59655